Maria Eliza Rundell (née Ketelby; 1745 – 16 December 1828) was an English writer. Little is known about most of her life, but in 1805, when she was over 60, she sent an unedited collection of recipes and household advice to John Murray, of whose family—owners of the John Murray publishing house—she was a friend. She asked for, and expected, no payment or royalties.

Murray published the work, A New System of Domestic Cookery, in November 1805. It was a huge success and several editions followed; the book sold around half a million copies in Rundell's lifetime. The book was aimed at middle-class housewives. In addition to dealing with food preparation, it offers advice on medical remedies and how to set up a home brewery and includes a section entitled "Directions to Servants". The book contains an early recipe for tomato sauce—possibly the first—and the first recipe in print for Scotch eggs. Rundell also advises readers on being economical with their food and avoiding waste.

In 1819 Rundell asked Murray to stop publishing Domestic Cookery, as she was increasingly unhappy with the way the work had declined with each subsequent edition. She wanted to issue a new edition with a new publisher. A court case ensued, and legal wrangling between the two sides continued until 1823, when Rundell accepted Murray's offer of £2,100 for the rights to the work.

Rundell wrote a second book, Letters Addressed to Two Absent Daughters, published in 1814. The work contains the advice a mother would give to her daughters on subjects such as death, friendship, how to behave in polite company and the types of books a well-mannered young woman should read. She died in December 1828 while visiting Lausanne, Switzerland.

Rundell was born Maria Eliza Ketelby in 1745 to Margaret (née Farquharson) and Abel Johnson Ketelby; Maria was the couple's only child. Abel Ketelby, who lived with his family in Ludlow, Shropshire, was a barrister of the Middle Temple, London. Little is known about Rundell's life; the food writers Mary Aylett and Olive Ordish observe "in one of the most copiously recorded periods of our history, when biographies of even the light ladies can be written in full, the private life of the most popular writer of the day is unrecorded".

On 30 December 1766 Maria married Thomas Rundell, either a surgeon from Bath, Somerset, or a jeweller at the well-known jewellers and goldsmiths Rundell and Bridge of Ludgate Hill in the City of London. The couple had two sons and three daughters.

The family lived in Bath at some point, and they may also have lived for a while in London. Thomas died in Bath on 30 September 1795 after a long illness. Rundell moved to Swansea, South Wales, possibly to live with a married daughter, and sent two of her daughters to London, where they lived with their aunt and uncle.

During her marriage and in widowhood, Rundell collected recipes and household advice for her daughters. In 1805, when she was 61, she sent the unedited collection to John Murray, of whose family—owners of the John Murray publishing house—she was a friend. It had been sixty years since Hannah Glasse had written The Art of Cookery Made Plain and Easy, and forty years since Elizabeth Raffald had written The Experienced English Housekeeper—the last cookery books that had sold well in Britain—and Murray realised that there was a gap in the market.